Convertibles with 3 point seat belt conversion?

Hello, I am getting to the nitty gritty with my 67 Dart Gt convertible restomod. I went with custom bucket seats and I would like to convert over to a 3 point seat belt system that has the shoulder strap. Has anyone done this? if so tell me about your process for making it work.
For what is't worth, here is what I did with my 69 Convertible. I used Cadillac CTS seats with the integral shoulder harness.
Bucket Seat Restomod: Cadillac CTS seats in a 69 Dart Convertible